Re: FUSE fusexmp proxy example solves umount problem!

Luke Kenneth Casson Leighton
2004-09-22T11:11:17Z

On Wed, Sep 22, 2004 at 11:33:30AM +0200, Arjan van de Ven wrote:
> On Wed, 2004-09-22 at 02:49, Luke Kenneth Casson Leighton wrote:
> > what do people think about a filesystem proxy kernel module?
> > has anyone heard of such a beast already?
> > (which can also do xattrs)
> >
> > fusexmp.c (in file system in userspace package) does stateless
> > filesystem proxy redirection.
> >
> > this is a PERFECT solution to the problem of users removing media
> > from drives without warning.
>
> eh and the 2.6 kernel doesn't deal with it? It really is supposed to
> deal with it nicely already...

okay.

the reason that fusexmp works is because it doesn't actually touch the
filesystem except on an operation: there's no state information stored,
no file handles kept open, no directory handles kept open.

an implementation of this same functionality (a filesystem proxy)
in the linux kernel would involve:

- creating proxy inodes

- reconstructing the full path name

d_path(dentry, mnt, full_path, sizeof(full_path));

then prefixing that with the mount point and then issuing a
proxy command.

now, if the solution to this problem in the linux kernel is broken
because someone forgot to deal with opendir() then _great_.

in the meantime...